The present invention relates to a composite core for the winding of web material. In particular the invention is directed to a sleeve for covering a cylindrical tube.
Web material, such as paper products and the like, is typically mechanically wound onto a rotating core member. Covers are commonly applied to winding web cores to improve the performance of the winding process. The use of a cover diminishes the occurrence of damage to the web during winding, thereby reducing the necessity to discard deformed webs. The covers deform on the outer surface to accommodate irregularities in the web.
Developments in the use of cores with covers resulted in several methods of application of plastic covers to core members. The application of heat or pressurized air to either the core or tube members changes their diameter, facilitating the overlapping connection of the two.
For example, U.S. Pat. No. 2,659,547 (Broadbent et al.) shows a cylindrical barrel covered by a sleeve, wherein the sleeve is heated to expand its dimensions sufficiently so that it can be slid over the barrel. As the sleeve cools, it contracts to form a tight fit between itself and the barrel. U.S. Pat. No. 3,289,973 (Spencer) shows a paper tube having a plastic sleeve slid over the outer surface of the tube, wherein the tube is heated to reduce its moisture content which, in turn, reduces the diameter of its outer surface. Once the diameter is reduced, the sleeve is slid over the tube. Thereafter, the tube absorbs moisture which expands its outer surface into frictional engagement with the inner surface of the sleeve.
Japanese Patent Publication No. 405201597 shows a fiberglass reinforced plastic cylinder having a coating of polyethylene on its outer surface. The coating may be obtained by covering the surface of the cylinder with a heat-shrinkable tube of ultra-high polymer polyethylene or by forming it directly on the surface of the cylinder.
U.S. Pat. No. 5,857,643 (Czuprynski et al.) shows a core for winding a web of material, wherein the core comprises a rigid cylindrical member over which is applied a deformable cover. To assemble the core, pressurized air is used to expand the cover so that it can be slid over the cylindrical member. U.S. Pat. No. 3,035,331 (Wieman) shows a resilient cylindrical body on which is mounted a non-stretchable sleeve. A vacuum is used to draw air out from the body to reduce its diameter so that the sleeve can be slipped over it. When the vacuum is disconnected the pressure within the body equalizes with the surrounding atmosphere and expands the body into tight frictional engagement with the sleeve.
The above cited patents have several drawbacks. First, the outer surface of the covers are generally not smooth. The outer surface of the covers have to be grinded down or smoothed before they can be used to wind certain web materials. Secondly, the prior art utilizes a rigid core and a flexible shrinkable sleeve. The composite core of the invention uses two rigid and sized members. The advantage of this is that a wide variety of materials can be used to manufacture the core and sleeve. The sleeve of the invention is heated to expand the sleeve, which teaches away from the ""597 Japanese publication. Thirdly, the covers are generally slight in thickness, to facilitate expansion and sliding over the underlying core. The xe2x80x9cthinxe2x80x9d covers reduce the stability of the core during winding, leading to irregularities in the web. Finally, to overcome the instability, end caps are commonly used to provide rigidity and strength to the core. However the end caps add to the time and labor costs of preparing cores for reuse.
The common use of cores in the winding of webs has created the need for strong, reusable and washable cores. The cores typically need to be cleaned between uses by immersing them in a solution. Additionally, many applications of the core winding member require that manufacturers of webs be able to match various web materials with different core winding properties.
The present invention is a reusable composite core or winding web material comprising a hollow cylindrical base tube which is covered by a sleeve. At room temperature, the sleeve has an inner diameter that is smaller than the diameter of outer surface of the tube, but larger than the inner diameter of the tube. The tube is made of fiber, paper, thermoplastic, fiberglass, polyester, a polyester-paper composite, or the like. The sleeve is made of an extruded thermoplastic material that is washable and stain resistant. The sleeve protects the tube""s outer surface from staining. The materials used for both the tube and the sleeve may be manipulated or finished to control the performance characteristics of the core.
To assemble the composite core, the sleeve is heated to expand the diameter of its inner surface so that it can be slid over the tube. Thereafter, the sleeve is allowed to cool to room temperature, which causes the diameter of its inner surface to contract into engagement with the outer surface of the tube, yielding a tight fit. Alternatively, the diameter of the outer surface of the tube may be reduced by cooling, drying or other techniques.